Waste recovery of thermoplastic continuous filamentary material

ABSTRACT

Apparatus for recovering waste thermoplastic fiber of continuous length filamentary material and converting it into re-useable feed stock and particularly a large otherwise unmanageable, entangled mass of continuous length filamentary material, some or all of which being either drafted or undrafted, wherein the continuous length filamentary material is converted into random length staple fiber, the staple fiber is then mechanically compacted and melted into a melt flow, and the melt flow is finally extruded as the re-useable feed stock.

United States Patent Hester et al. [4 Nov. 21, 1972 [54] WASTE RECOVERYOF 3,517,097 6/1970 Mixell et a]. ...........18/12 R X THERMOPLASTICCONTINUOUS 3,551,943 1/1971 Staton et al. ..18/ 12 R X FILAMENTARYMATERIAL 2,589,323 3/1952 Ashby et a1. ..18/12 R [721 Robert "9 HowardPierson, 5:35:32 151323 2252211222 1.51325 bmh Kmgspm- 3,233,022 2/1966Henry et al ..18/1 B ux 73 Assignee; E t Kodak Company 3,61 1,48910/1971 Morozov et a1. ..18/ 12 R Rochester, NY. Primary ExaminerRobertL. Sp1cer, Jr. [22] Ffled: 1970 AttorneyCecil D. Quillen, Jr. andMalcolm G. Dunn [21] Appl. No.. 67,324 [57] ABSTRACT [52 us. 01...425/67, 425/113, 425/202, Apparatus for recovering Waste thermoplasticfiber of 425/208 continuous length filamentary material and converting51 1111.01 ..132911 7/02, B291 3/02 it re-useable feed Stock andparticu'arly a large Field of Search P 30 FR 4 l B, otherwiseunmanageable, entangled mass Of COIltiilll- Y 13 7, 0118 lengthfilamentary material, some 01' Of WhlCh 214/17 being either drafted orundrafted, wherein the con tinuous length filamentary material isconverted into random length staple fiber, the staple fiber is then [56]References Cited mechanically compacted and melted into a melt flow,UNITED STATES PATENTS and the melt flow is finally extruded as there-useable feed stock. 3,192,293 6/1965 Van Riper ..18/DlG. 46 3,344,2129/1967 Francis ..18/DlG. 46 12 Claims, 10 Drawing Figures PATENTEnmm meI 3.703.347

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ATTORNEY P'A'TE'N'TEDNM I m2 sum 8 or 8 ROBERT HESTER HOWARD F. PIERSONINVENTORS ATTORNEY WASTE RECOVERY OF THERMOPLASTIC CONTINUOUSFILAMENTARY MATERIAL BACKGROUND OF THE INVENTION The present inventionis directed to an apparatus by which waste thermoplastic fiber ofcontinuous length filamentary material, andparticularly a largeotherwise unmanageable, entangled mass of continuous length filamentarymaterial, some or all of which being either drafted or undrafted, may berecovered and converted into re-useable feed stock without lowering theinherent viscosity (I.V.) to any substantial degree and without creatingpoor color in the re-useable feed stock, and to the resulting product ofthe process.

In the spinning and processing of man-made fibers, such as fibers ofthermoplastic materials, there is usually a large amount .of wastecreated, which is due to a number of reasons. Such waste may be duetoroll wraps; from starting up a processing line; or as a result ofmalfunctions in some of the processing equipment. The fiber waste isusually in continuous lengths, and may either be lubricated ornon-lubricated, depending at which stage of the processing the wasteoccurred.

Attempts have been made to segregate the lubricated waste fiber from thenon-lubricated, and then baling each type for subsequent disposition.Sometimes these attempts have not been successful, especially if thewaste occurs over an area of a processing line including a lubricationbooth with the result that part of a waste length would benon-lubricated, and the other part would be lubricated. In the lattersituation it is not economical to attempt to cut one portion from theother as it is more vital that the operators on a processing line getthe operating line back into operation and make certain that the fiberspassing along the processing line are moving as they should.

One manner of handling the waste bales of fibers previously has been toburn them since no successful and commercially practical manner ofrecovering the waste material wasknown. The fiber and any lubricants inthe fiber have created quite a pollution problem, and thus presentedundesirableconditions as well as making prohibitive the cost of thefacilities and personnel for handling the burning.

Another manner employed was to store the bales until some commerciallyeffective method was developed for recovering the waste. In themeantime, however, since each bale weighs in the vicinity of about 500pounds, storage space became a serious and costly problem, as well asbeing costly to move the waste bales from the processing lines to thestorage area.

Still another manner involved using the waste for land fill.

Various approaches have been investigated for recovering the waste fiberin an attempt to re-use it, but these have usually been disadvantageouseither due to being too expensive and thus not commercially practical,or the degradation of the material was such that the resulting productwas of inferior quality and color.

One approach with respect to polyester waste such as polyethyleneterephthalate (PET) waste, has been to treat fiber waste withsuperheated steam at a temperature below the melting point of thepolyester as disclosed in US. Pat. No. 3,098,046. The fiber waste sotreated becomes brittle and then can be reduced to a powder form. Thepowdered PET is next suspended in a liquid medium, such as methanol orglycol, and the resulting dimethyl terephthalate is then used again forthe production of a polycondensation product.

Another approach as disclosed in Defensive Publication T870,0l0,published Jan. 13, 1970 in the Official Gazette of the United StatesPatent Office (870 0.6.3933), is to pass the waste PET tow lengthsthrough a tow dryer and to raise the temperature from a normal C. toabout 215 C. The result is that the waste tow becomes highlycrystallized and brittle. This material is then passed through ahammermill and reduced to particles. The resulting product, however, hasa low bulk density of about 15 to 20 pounds per cubic foot, whereasvirgin polymer powder has a bulk density of about 50 pounds per cubicfoot. One reason for the low bulk density is that there is still somefibrous-like material in the product; also the particles are notentirely reduced to powder. It is very expensive and time consuming tocontinue processing the material in the hammermill until it is totallyreduced to powder. It is difficult to blend the resulting material oflower bulk density in with virgin polymer powder. The extruder intowhich the powder is fed for melt extrusion into a fiber is designed totake the higher bulk density virgin polymer powder, but the recoveredlower bulk density material cannot be fed into the extruder fast enoughto fill up the extruder screw flights so as to maintain a constant feed.

Additionally, a certain amount of undesirable color is introduced, andthe recovered material still has a certain amount of lubricant remainingso that it is not possible to spin a first quality fiberfill which canbe used for such things as matresses, pillows and air filters.

When attempt was made to recover waste polyester materialofpoly(l,4-cyclohexylene dimethylene terephthalate) (PCHDMT), the passingof the waste material through the tow dryer at the required elevatedtemperature, such as 265 C., the material was caused to becomeundesirably brown in color, and thus was not suitable for commercialuse.

In attempts to reduce the waste materials by use of chemicals, the costof the chemicals was too much and the process was found to be too costlyto operate.

Accordingly, one of the objects of the invention is to provide anapparatus for recovering waste thermoplastic fiber of continuous lengthfilamentary material in an economical and expeditious manner, whereinthe continuous length filamentary material is converted into staplefiber, the staple fiber is mechanically compacted and melted into a meltflow, and the melt flow is finally extruded as a re-useable feed stock.

Other objects inherent in the nature of the invention will becomeapparent to those skilled in the art to which this invention pertainsfrom the drawings and description that follows.

SUMMARY OF THE lNVENTION The invention, therefore, is directed toapparatus for recovering waste thermoplastic fiber of continuous lengthfilamentary material and particularly a large otherwise unmanageable,entangled mass of continuous length filamentary material, some or all ofwhich being either drafted or undrafted, and converting it intore-useable feed stock. The continuous filamentary material is convertedinto random length staple fiber or staple fiber of predeterminedlengths, the staple fiber is mechanically compacted and melted into amelt flow, and the melt flow is subsequently extruded as re-useable feedstock.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a perspective view of the apparatus for recovering wastethermoplastic fiber, with portions of the structure removed toillustrate the working parts;

FIG. 2 is elevational view in cross section of the storage bin;

FIG. 3 is a fractional view enlarged of the doffer comb used in thestorage bin;

FIG. 4 is a perspective view of the extruder with portions broken awayand illustrating the feed section and a portion of the feed screw;

FIG. 5 is a fractional view in cross section taken along line 55 in FIG.4 and illustrating the fiber being fed into the feed section;

FIG. 6 is a view in cross section of the extruder barrel andillustrating the feed screw, the heaters, and further illustratingremoved from extruder barrel the feed screw as related to the varioussections of the extruder with the profile of the extruder barrel beingshown in phantom lines;

FIG. 7 is an enlarged perspective view of the feed screw and theremovable feed section insert, illustrating in part the wedged keysection;

FIG. 8 is an enlarged cross-sectional view of the feed section insert;

FIG. 9 is a development of the feed section insert to illustrate thearrangement of the wedged keys; and

FIG. 10 is an exploded perspective view enlarged of portions of theunderwater pelletizer.

DESCRIPTION OF THE PREFERRED EMBODIMENT In reference to FIG. 1 theapparatus illustrated at 10 includes a baler l2 and guillotine 14, afirst rotary cutter 16, a second rotary cutter 18, a storage and holdupbin 20, an extruder 22, an underwater pelletizer 24, and a centrifugaldryer 26 for the extruded pellets.

The waste fiber may be collected from the various processing lines inwaste buggies, such as the one illustrated in FIG. 1 at 28. The buggieswill each hold several hundreds of pounds of continuous filamentarywaste in a large bulky, entangled mass, some or all of which beingeither drafted or undrafted, and lubricated or non-lubricated, which isthen dumped into the baler 12, preferably through the top of the baler,and compressed into a bale of predetermined size.

The guillotine 14 when in the lowered or cutting position serves tocontain the waste when it is dumped through the top of the baler, andwhen actuated cuts the bale into sections while a ram (not shown) withinthe baler moves the bale toward the guillotine in increments of about 4to 6 inches. The severed sections (not illustrated) drop onto a conveyorbelt 30 located adjacent the guillotine, and the belt conveys thesevered sections to the first rotary cutter 16 wherein the sections arefurther cut and reduced in size, and then the output of the first rotarycutter is dropped onto another conveyor belt 32 which serves to conveythe output to the second rotary cutter 18. The latter rotary cutterfinally reduces and converts the waste material into staple fiber ofabout the same predetermined lengths or random lengths.

The staple fiber falls from the second rotary cutter onto conveyor belt34 for subsequent conveying to the storage and hold-up bin 20.

Polyester continuous length fiber waste is extremely tenacious. Thesections of the bale cut by the guillotine, even though the sections areonly in 4 to 6 inch increments, may contain groups of individual lengthsof fibers that are many feet long. Thus reliance upon the cut made bythe guillotine is not sufficient to enable the material to be readilyhandled by the extruder. The single rotary cutter following theguillotine was found to be somewhat effective, but the addition of asecond rotary cutter proved to make the overall process most effectivein cutting and reducing the fiber to a manageable size, such as a randomlength staple fiber having a length of about 3 inches. This length is anapproximation since some staple fiber will be less than this, and somewill be perhaps as much as 6 inches in length. It has been found,however, that this approximate length of staple fiber can subsequentlybe fed into the extruder 22 without bridging over the opening andblocking other fiber from being fed to the extruder.

The series of cutting steps that are described above thus serve toconvert the continuous length filamentary material into staple fiber.

Another manner of converting such continuous length filamentary materialinto staple fiber would be to use a stretch-break process, but thiswould require a suitable handling of the waste material so as to feedthe material in continuous length form and to maintain continuity offeed.

Still another manner would be to feed the continuous length filamentarymaterial to a fearnaught or fearnought machine that would shred and pullthe waste material apart until the material is converted into staplefiber.

In viewing FIG. 2, the staple fiber 36 passes from the conveyor belt 34into the storage and hold-up bin 20. The latter is provided therein withtwo separate apron conveyors 38, 40. Apron conveyor 40 is provided witha series of spikes, as shown for instance at 42, and which project fromwooden slats 43. The two apron conveyors convey the collected staplefiber from the inlet opening 44 of the storage bin to the outlet opening46 in a controlled manner, as will be described hereinafter.

The storage bin that has proved to be most effective is what is known inthe trade as a Hunter blender, or any equivalent make, manufactured bythe Hunter Machinery Company. This blender was modified by removingabout two-thirds of the spikes and the slats from which these spikesprojected so that the spacing between adjacent spiked slats is about 5inches. This was done in order to prevent the staple fibers frombecoming interlocked with the spikes on adjacent slats, and thusminimize the tendency of the fiber to cling to the apron conveyor. Theblender was further modified by slowing the speed of the two apronconveyors 38, 40 so as to avoid overfeeding of the staple fiber. Suchoverfeeding would otherwise result in tumbling back of the fiber andthereby cause undesirable roping and knotting of the staple fiber.

The first apron conveyor 38 is also provided with a plurality of slats45 which are not spiked. This conveyor serves to maintain continuity offeed of the staple fiber to the second apron conveyor 40.

Maintaining continuity and control of the feed to the extruder isessential to effective operation of the overall process. One manner ofcontrolling the feed is to regulate the speed of the two apron conveyors38, 40 in the storage bin by the operator who makes the necessary speedadjustments when he observes that there is either too much or too littlestaple fiber being fed into the extruder. Another manner of regulatingthe speed of the two apron conveyors is in response to an ammeter (notshown) connected to the extruder and which indicates whether the load onthe extruder feed screw is too much or too little.

A comb doffer 48 is located adjacent the top of apron conveyor 40 andthe outlet opening 46 of the storage bin. The comb doffer brushes thestaple fiber from the apron conveyor 40 onto a conveyor belt 50, asillustrated in FIG. 2. As indicated by the arrows in FIG. 2, the combdoffer oscillates between two positions relative to the top of the apronconveyor 40. As may be seen in FIG. 3, the comb doffer is provided witha slotted member 49 which clears the spikes 42 and lifts any staplefibers adhering thereto.

An additional cornb doffer 47 may be optionally provided adjacent apronconveyor 40, and which may be caused to oscillate, as shown by thearrows in FIG..2, to

I preclude the possibility of too much staple fiber from moving up tothe outlet opening 46.

The storage bin is thus capable of receiving more staple fiber than ismetered out to the eXtruder; serves to receive and to store the staplefiber; and serves to control and to regulate the feed or metering of thestaple fiber through the outlet opening to the extruder and therebyassures and maintains continuity of feed to the extruder.

The conveyor belt 50 carries the staple fiber to the extruder 22, andpasses under a metals detector unit 52 (FIG. 1), which operates in awell-known manner to detect any metal, which may inadvertently have beencollected with the waste fiber, and to cause the conveyor belt to stopmoving upon such detection. The metals detector unit thus prevents anymetals from entering via the storage bin and damaging the extruder.Conveyor belt 50 is provided with flexible corrugated sidewalls ortroughs 59 (FIGS. 4, 5), such as made by the Bucket Elevator Companythat prevent the fiber from falling from the belt. Polyester fiber, forinstance, can readily slip or spill from a moving conveyor unless somemeans is provided to contain it on the conveyor.

The staple fiber is delivered from conveyor 50 into the watercooledjacketed feed section 54 of the extruder 22 through an elongatedtangential side opening 56 whereupon the fiber drops onto a downwardlyinclined surface 58. The latter surface enables the staple fiber to befed directly toward the bite of the feed screw 60; the bite defined asbeing between the downwardly turning portion of the feed screw and theinterior wall or downwardly inclined surface 58 of the extruder barrel62 (FIG. 5). The feed .section is jacketed (FIGS. 5, 6) so as tocirculate water within the jacket in the area designated 55. The waterserves to cool the interior wall surfaces of the feed section andespecially the downwardly inclined surface 58. During the operation ofthe extruder, heat from the portion of the extruder that is forward ofthe feed section will be conducted back to the feed section through thefeed screw 60. The heat emanating from the feed screw will tend to heatthe interior wall surfaces of the feed section. It is thereforenecessary to cool the interior wall surface and particularly thedownwardly inclined surface 58 so as to prevent the staple fiber fromsticking to the downwardly inclined surface. If the staple fiber sticksto the latter mentioned surface, other incoming staple fiber will merelycollect on top of the stuck fiber and will quickly bridge over theopening to the feed section, thereby preventing further feed of staplefiber to the bite of the feed screw.

The tangential side opening, the downwardly inclined surface and thejacketed feed section are essential for the success and effectiveness ofthe invention. Previously, it has not been possible to feed staple fiberinto an extruder. The fiber would bounce along on 1 top of the feedscrew, and other fiber fed on top of the first fed fiber would merelypile on top and bridge across the opening and thereby prevent additionalfiber from being fed into the extruder.

Also essential for the effectiveness of the invention is that theelongated tangential side opening 56 should be about two times as longas the diameter of the feed screw as a minimum, and preferably aboutthree times the diameter. Thus, if the feed screw should be 6 inches indiameter, the side opening would be about 18 inches long.

Another difficulty previously encountered in feeding staple fiber intoan extruder is that once the feed screw had accepted the fiber, thefiber would not move forward along the length of the extruder barrel.Instead, the fiber would collect as a wad of material around the shaftof the feed screw and would stay in about the same place rotating withthe feed screw. This difficulty was solved by providing in the feedsection of the extruder a keyed section or insert 64 having keyed wedges66. The keyed wedges extend radially inwardly from the interior wallsurface of the keyed section or insert 64, and are circumferentiallyspaced apart and are also spaced from the feed screw 60. As may be bestseen in FIGS. 8 and 9, the keyed wedges initially spiral around andalong a portion of the length of the feed section, and then straightenso as to extend parallel to and for the remainder of the feed section.

The keyed wedges in the feed section cooperate with the feed screw toassure forward feeding of the staple fiber and to prevent the fiber fromremaining in one location in a wadlike form around the feed screw andthereby rotate with the feed screw. The keyed wedges serve to provideresistance to the turning of the staple fiber, and thus the flights 68of the feed screw can then move the staple fiber forward.

The initial spiraling of the keyed wedges prevents the staple fiber frombeing sheared with the possible result of filling up solid the spacesbetween adjacent keyed wedges and therefore being beyond the reach ofthe feed screw flights, which could otherwise push the material forward.

The keyed wedges, their particular disposition and arrangement, and incooperation with the flights of the feed screw, thus serve to maintainmovement of the mass of the staple fiber perpendicular to the feed screwflights rather than at an inclined angle which would otherwise tend topromote the undesirable shearing mentioned above. When the mass of thestaple fibers is essentially perpendicular to the feed screw flights,the latter can then effectively move the staple fibers forward. Once thestaple fibers have been given their initial impetus, the mass of staplefiber coming from behind serves to keep the mass that is forward thereofmoving. Thus the shear that may occur forward of the initial spirallingof the keyed wedges will be of no consequence since the mass of staplefibers coming from behind will assure movement of all of the materialthat is forward thereof. An advantage of this arrangement is that nomaterial will be left undesirably too long in one place and otherwisebecome degradated due to undesirable over-exposure to heat. Suchover-exposure would not only affect the I.V. but also the color of theultimate product.

Although the keyed section is shown as being a separate unit or insert64 that may be fitted within the extruder in the feed section 54, thekeyed wedges may also be formed integral with the extruder. Certainadvantages, however, accrue by having an insert. For instance, if forsome reason any metal should fall into the opening of the extruder, itwould be easier to repair damage to the insert by replacing it ratherthan replacing the entire feed section. Damage to the feed screw and itsflights would be repaired in conventional manner. Another reason: If thecharacteristics of the staple fiber should differ from one type toanother, a change of the insert for one having keyed wedges of adifferent size or width, or even disposition of the wedges, couldreadily be made.

When the staple fibers are moved by the feed screw forward of thetangential side opening 56 and into the enclosed portion of the feedsection, mechanical compaction of the fibers commences. The rootdiameter of the feed screw is of constant size in the area of the feedsection, such area or first section being designated at A in FIG. 6 ofthe drawings. The interior wall surface of the feed section tapersinwardly toward the feed screw at a location adjacent the tangentialside opening, as shown at 70 in FIG. 6. The taper reduces the volumebetween the feed screw and the extruder barrel and thereby aidsmechanical compaction. The flights on the feed screw, combined with thetaper of the feed section, have a compaction ratio of about :1, whichwill thus serve to assure exclusion of essentially all of the air.

In the second area or second section, designated B in FIG. 6, heat isapplied from the extruder barrel by means such as the electric heaters72, 74 and 76. The root diameter of the feed screw tapers radiallyoutwardly thereby further reducing the volume between the feed screw andthe extruder barrel and thus increasing mechanical compaction. It is inthis area that it is thought that conversion into a melt flow commencesand without the presence of air. Also, it is thought that most of thevolatiles and moisture in the form of vapor are removed through theopening in the feed section by virtue of the drying action occurring inthe initial stages of the compaction. The compacted staple fiber'orcompacted material is moved by the feed screw relative to the hot barrelinterior surface, the latter surface serving to melt that portion of thecompacted material that is in contact with the surface and therebyforming a molten fluid film. The fluid film along with the hot interiorwall surface generates further melting of the compacted material due toviscous heat generation in the molten fluid film above the compactedmaterial. This commences a phase transition area or melting area inwhich the solid polymer or the compacted material and the molten fluidfilm coexist.

The heat generated by electric heater 72 is in the temperature range ofabout 490 to 540 F. for a staple fiber such as from PET; and in therange of about 530 to 550 F. for a staple fiber such as from PCHDMT.

Electric heater 74 generates heat in the temperature range of about 520to 550 F. for PET fibers; and in the range of about 580 to 600 F. forPCI-IDMT fibers.

Electric heater 76 generates heat in the temperature range of about 405to 520 F. for PET fibers; and in the range of about 530 to 550 F. forPCHDMT fibers.

In the third area or section, designated C in FIG. 6, the root diameterof the feed screw and the inside diameter of the interior wall surfaceremains constant. The phase transition is still in progress, andpressure is being increased in the melt flow.

A ring valve 78 is provided at the end of the third section C and servesto prevent solid material from passing therebeyond in gross amounts, andit also enables operation of the first stage metering zone, as includingsections A, B and C, at higher pressures. The ring valve further servesto cooperate to prevent flooding the vent 80.

The ring valve is adjustable in a conventional manner so as to regulatethe spacing between the ring valve and the barrel interior wall surface.Such adjustment serves to regulate the back pressure in the first stagemetering zone, and to determine the rate of flow of the melt flow pastthe ring valve. It also assures that essentially no unmelted particleswill pass thereby. For a further description of a ring valve, referencemay be made to Heston US. Pat. No. 3,475,787.

In the fourth area or section, designated D in FIG. 6, any remainingvolatiles are vented through vent 80. The flights 82 are so arranged toenable exposure of more polymer surface area for more efficientdisengaging of gaseous products. The flights are only partially filledwith the melt flow so as to enable the disengaged gas to reach the ventopening. This section may operate at about zero gage pressure oratmospheric pressure. If desired, the section also may be operated undera vacuum.

The fifth area or section, designated E, and the sixth area or section,designated F, in FIG. 6, together constitute the second stage. As may beseen in FIG. 6, the root diameter of the feed screw in the fifth sectionE tapers radially outwardly, but is reduced in overall diameter fromthat of the preceding section in order to prevent flooding of thepreceding vent section. Probably, more disengaging of the gaseousproducts occurs in the fifth section. Also, pressure is being built upin the sixth section and possibly the fifth section sufficient to pumpthe melt flow or molten polymer through the die of the underwaterpelletizer 24.

The electric heater 84 in the fifth section generates heat in thetemperature range of about 400 to 520 F. for PET fibers; and in therange of about 530 to 550 F. for PCI'IDMT fibers.

The electric heater 86 in the sixth section generates heat in thetemperature range of about 390 to 520 F. for PET fibers; and-in therange of about 530 to 550 F. for PCHDMT fibers.

The temperature in each of the electric heater sections is regulated byfans designated at 88, 90, 92, 94

t and- 96 which force cooling air around the outside of the extruderbarrel through the jacketed areas designated at 98, 100, 102, 104 and106. This control is essential to prevent a build-up of heat as thecompacted material continues to melt and thereby minimizes possibledegradation of the melt flow.

The molten polymer or melt flow passes through a screen and screenadapter, which are not specifically illustrated other than at theportion designated at 108 in FIGS. 1 and 6. Block induction heaters (notshown) are provided for the screen and screen adapter as well as thespare screen and screen adapter (not shown) so as to maintaintemperatures within certain ranges. The screen will be maintained in therange of about 390 to 520 F. for PET fibers; and in the range of about530 to 550 F. for PCHDMT fibers. The screen adapter will be maintainedin the range of about 400 to 520 F. for PET fibers; and in the range ofabout 530 to 550 F. for PCHDMT fibers.

The molten polymer or melt flow is pumped from the extruder 22 to theunderwater pelletizer 24 through a connecting pipe or adapter section109 (FIGS. 1 and 6) that is suitably heated by a band heater (notshown), the underwater pelletizer being shown in more detail in FIG. 10.s

In reference to FIG. 10, therefore, the melt flow enters the pelletizerbody 110 through inlet 112 and around annular channel 113 for extrusionthrough the orifices 114 of die plate 116. A- hot high temperature heattransfer liquid or fluid such as Monsantos THER- MINOL 77 fluid iscirculated through channels 118 located on one side of the die plate soas to heat the die plate and promote flow of the polymer through the dieplate. The die plate is retained in position against the pelletizer body110 by a retainer or support plate 120. A rotatable knife 122 and hub124 are supported for rotation by a shaft (not shown) which extendsthrough opening 126 in the die plate and opening 128 in the pelletizerbody and which is suitably connected for driven rotation to a motor 130(FIG. 1) located above the pelletizer. A water housing 132 is providedwithin which heated water is circulated against the other side of thedie plate. The housing is held in position against the retainer plate120 by bolts and wing nuts shown at 134. The circulating hot waterenters the water housing through inlet 136 and into contact against theface of the die plate. The water and pellets, as formed by the revolvingknife when the molten polymer is extruded through the orifices andsheared by the knife, exit as a slurry through exit opening 138. Theslurry then flows to the centrifugal dryer 26 through a pipe 140(fragmentarily shown in FIG. 1). U.S. Pat. No. 3,477,098 describes onetype of centrifugal air dryer used in connection with an underwaterpelletizer, and reference may be had to this patent for a betterunderstanding of centrifugal dryers. The pellets then may pass to astorage silo (not shown) after the water is removed and maintained undera suitable inert gas.

The temperature of the heat transfer fluid is in the range of about 570to 770 F. forPET polymer; and'in the range of about 580 to 800 F. forPCHDMT polymer.

The temperature of the hot circulating water is in the range of about to200 F. for PET polymer; and in the range of about to 210 F. for PCHDMTpolymer.

The resulting I.V. (Inherent Viscosity) of the finished pellets orre-useable feed stock is about 0.45 to 0.55 for PET; and is about 0.45to 0.68 for PCHDMT. This compares approximately to an I.V. of about 0.60:1: 0.02 for virgin PET pellets, and to an I.V. of about 0.785 t 0.02for virgin PCHDMT pellets.

The following table lists a comparison of properties that the re-useablefeed stock has in comparison to virgin feed stock from which there-useable feed stock is subsequently derived.

TABLE Virgin Feedstock Re-useable Feedstock PET PCHDMT PET PCHDMTinherent viscosity .60L02 1851.02 .45to.55 .45to.68 801-5 77.5:4 colorR*SD 87-5 *"83+4-2 *B 871-3 "84+3 +1.8:l .5tl an "SD +lil "lil "B .5:]**-1:tl

+.5tl +5i2 *SD -3.5:1.5 ***+4:1.5 "'13 +5.5: l-2 Fl-4:15 melting point(DSC)"" 252Ct3 29ICi4 255Cfi 290C16 *Semi-dull (0.20% i .02% TiO *Bright(No TiO,)

* *Semi-dull (0.32 102% Ti0,)

* Differential Scanning Calorimeter The color R a and b are lightreflectance readings made on a Gardner Automatic Color Difference Meter,the latter being manufactured by Gardner Laboratory, Inc. R is definedas one hundred times the amount of light reflected by a sample dividedby the amount of light reflected by a perfectly diffusing sample(actually by magnesium oxide), when the light is incident upon thesample at an angle of 45 and the measuring device records the lightdiffused perpendicularly from the same or at 0. A completely absorbingspecimen or sample would have a R; value of 0, and a perfect diffusingwhite would have a value of 100. Thus the higher the value, the whiterthe sample.

The a and b values are chromaticity coordinates. A plus a equalsredness; a minus a equals greenness; a plus b equals yellowness; and aminus b equals blueness. More greenness and more blueness is preferredwith respect to the two particular polyesters mentioned herein.

No distinction is made in the table between semi-dull and brightpolyester in the re-useable feed stock since no attempt was made tosegregate the two types of waste continuous filamentary material; thusthe readings for re-useable feed stock may or may not be a composite ofsemi-dull and bright polyester, depending upon the runs that were madeand the extent of waste generated at the time of the runs.

The percentages of TiO are only representative of one type of semi-dullpolyester, and the color reflectance readings would differ with the useof other percentages of TiO;.

An advantage of the above-described system of waste recovery is that itis no longer necessary to segregate lubricated waste filamentarymaterial from non-lubricated material, nor is it necessary to remove theyarn lubricant from the waste material before passing the material intothe system for recovery of the re-useable feed stock. vaporized waterand oil may escape through the opening in the feed section and throughthe vent 80.

Another and still more significant advantage is that bulky, otherwiseunmanageable mass of continuous length filamentary materials may bereadily handled, and even though such material may be in the drafted orundrafted state or be a combination of either state, and even though thematerial may be either in a lubricated or non-lubricated condition or bea combination of either condition.

Furthermore, the waste continuous length material may be readilyprocessed by the arrangement disclosed herein without the necessity ofpre-treating the material in any manner, such as by pre-drying toeliminate moisture because drying is accomplished in the feed sectionand in the initial stages of compaction and the resulting vapors areessentially removed through the opening in the feed section.

Although a system could be used in which the molten polymer wouldextrude through a die as a series of strands at the end of the extruderand into a water bath to be subsequently cut into pellets, theunderwater pelletizer is preferred because of the advantages it offers.For instance, the resulting product is more uniform and attractive, anddoes not have to be classified. Another advantage is that there is lessexposure of the finished product to atmospheric contaminants, if anycontaminants were to be present. Still another advantage is that thereis no exposure of molten polymer to the atmosphere, and thus there is apotential color improvement in the final product. A further advantage isthat there are less fines or dust particles due to the absence of sharpcorners on the pellets. A still further advantage over the extrusionstand arrangement is that the latter is difficult to set up if the feedof the staple fiber into the extruder should be lost for any reason.

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention.

We claim:

1. Apparatus for recovering waste thermoplastic fiber of continuouslength filamentary material and converting it into re-useable feedstock,and comprismg:

means for converting said continuous length filamentary material intostaple fiber;

storage means for receiving and storing said staple conveyor means formoving said staple fiber to said storage means from said means forconverting said continuous length filamentary material;

said storage means having an inlet through which the staple fiber isreceived and an outlet through which the staple fiber leaves the storagemeans, a conveyor means within the storage means for moving the staplefiber from the inlet to the outlet;

an extruder for compacting and melting said staple conveyor means fordelivering said staple fiber to I said extruder from said storage means;

said extruder having at one end a feed section adapted to receive saidstaple fiber and a feed screw that extends the length of the extruderand feed section;

said feed section defining an elongated tangential side opening throughwhich said staple fiber is introduced, and having a downwardly inclinedsurface that extends from said tangential side opening and to a locationtangentially adjacent said feed screw and adapted to conduct said staplefiber into the bite of the feed screw as defined therebetween by thedownwardly turning portion of the feed screw and said downwardlyinclined surface;

said feed section further being jacketed and thereby adapted to becooled by a circulating fluid medium so that the feed section interiorwall surface with which the staple fiber comes into contact is below thetemperature at which the staple fiber would tend to stick to saidinterior wall surface;

said feed section still further having a plurality of keyed wedgesextending radially inwardly from the interior wall surface of the feedsection and circumferentially spaced apart and spaced from said feedscrew, said keyed wedges initially spiralling partly around and along aportion of the length of the feed section and then straightening out toextend parallel to and for the remainder of said length of the feedsection, the keyed wedges adapted to cooperate with said feed screw toprevent said staple fiber from rotating with said feed screw and toassure continuous forward feeding of the staple fiber from thetangential side opening;

said extruder having heating means extending along the length of theextruder forward of the feed section for melting said staple fiber intoa melt flow and means for forcing cooling air around the outside of theextruder so as to regulate the heat applied to the staple fiber;

extrusion die means comprising an underwater pelletizer defining aninlet for receiving said melt flow, a die through which the melt flow isextruded, means for circulating a heated fluid through said die tomaintain a predetermined temperature, means for circulating a coolingfiuid on the extrusion side of the die to cool the melt flow whenextruded through the die, shearing means for shearing melt flow intopellets when the melt flow is extruded through the die, and outlet meansadapted to conduct therethrough the extruded pellets and cooling liquidas a liquid slurry;

means connecting the extruder and the extrusion die means and adapted toconduct said melt flow from one to the other; and

means following the underwater pelletizer and adapted to receive saidliquid slurry from said outlet means and remove the liquid from and drysaid pellets.

2. Apparatus for recovering an entangled mass of waste thermoplasticfiber of continuous length filamentary material and converting it intore-usable feed stock, and comprising:

means for compressing said entangled mass of continuous lengthfilamentary material into a mass of predetermined size; means forcutting said mass of predetermined size into sections of predeterminedsize, and further means for cutting said sections into staple fiber;

extruder means for mechanically compacting and melting said staple fiberinto a melt flow, and extruding said melt flow into said re-useablefeedstock; said extruder means having a barrel and a feed screwrotatable within said barrel, said barrel having connected at one end anextrusion die means and at the other end including a feed section, andbeing provided with heating means along its length; said feed sectiondefining an elongated tangential side opening through which said staplefiber is introduced into the bite of the feed screw, as definedtherebetween by the downwardly turning portion of the feed screw and theinterior wall of the barre]; and means for feeding said staple fiber toand into said tangential side opening and into the bite of the feedscrew thereby entrapping the staple fiber on the underside of the feedscrew and including means for controlling and metering the feed of saidstaple fiber;

said feed section further including therewithin means for preventingsaid staple fiber from rotating with said feed screw and thereby adaptedto enable and assure continuous forward movement of the staple fiberfrom the feed section to said extrusion die means.

3. Apparatus according to claim 2, and wherein the extruder meansfurther comprises:

means for internally cooling said feed section of the barrel so that thefeed section interior wall surface with which the staple fiber comesinto contact is below the temperature at which the staple fiber wouldtend to stick to said feed section interior wall surface.

4. Apparatus according to claim 2 and wherein said extrusion die meanscomprises an underwater pelletizer including a die, means located on oneside of the die to heat the die, and means on the other side of the dieto circulate heated water against the face of the die.

5. Apparatus according to claim 2 and wherein said means for controllingand metering the feed of said staple fiber includes a storage binadapted to receive and store more staple fiber than can be fed directlyto said extruder means for mechanically compacting and melting saidstaple fiber, said storage bin having inlet and 14 outlet openingsthrough which the staple fiber moves, and including therewithin conveyormeans for moving the stored fiber from the inlet opening to the outletopening and means for controlling the amount of staple fiber that movesthrough said outlet means.

6. Apparatus according to claim 2 and wherein said means for preventingsaid staple fiber from rotating includes surfaces extending radiallyinwardly from the interior wall of the feed section nd b ferentiallyspaced apart and adapted to c p erz t e v i rii h the flights on saidfeed screw to keep the movement of the mass of staple fibersperpendicular to the screw flights.

7. Apparatus according to claim 2 and wherein said means for preventingsaid staple fiber from rotating includes a keyed section extendingradially inwardly from the interior wall surface of the barrel andspaced from said feed screw, said keyed section initially spirallingpartly around and along a portion of the length of the feed section andthen straightening out to extend parallel to and for the remainder ofsaid length of the feed section.

8. Apparatus according to claim 2 and wherein said means for preventingsaid staple fiber from rotating includes a plurality of keyed wedgesextending radially inwardly from the interior wall surface of said feedsection and circumferentially spaced apart and spaced from said feedscrew, said keyed wedges each initially spiralling partly around andalong a portion of the length of the feed section and then straighteningout to extend parallel to and for the remainder of said length of thefeed section.

9. Apparatus according to claim 7 and wherein said feed screw hassubstantially coextensive with said tangential side opening a firstsection having a root diameter of constant size, the interior wallsurface adjacent to said first section and to said side opening taperinginwardly toward said feed screw and thereby adapted in cooperation withsaid feed screw to initiate compression of said staple fiber.

10. Apparatus according to claim 7 and wherein a downwardly inclinedsurface extends from said elongated tangential side opening toward saidbite of the feed screw, said inclined surface adapted to conduct saidstaple fiber into said bite when the fiber is introduced into said sideopening.

11. Apparatus according to claim 2 and wherein said tangential sideopening has a length about three times the diameter of the feed screw.

12. Apparatus according to claim 2, and wherein a downwardly inclinedsurface extends from said tangential side opening toward said bite ofthe feed screw, said inclined surface adapted to conduct said staplefiber into said bit when the fiber is introduced into said side opening.

1. Apparatus for recovering waste thermoplastic fiber of continuouslength filamentary material and converting it into reuseable feedstock,and comprising: means for converting said continuous length filamentarymaterial into staple fiber; storage means for receiving and storing saidstaple fiber; conveyor means for moving said staple fiber to saidstorage means from said means for converting said continuous lengthfilamentary material; said storage means having an inlet through whichthe staple fiber is received and an outlet through which the staplefiber leaves the storage means, a conveyor means within the storagemeans for moving the staple fiber from the inlet to the outlet; anextruder for compacting and melting said staple fiber; conveyor meansfor delivering said staple fiber to said extruder from said storagemeans; said extruder having at one end a feed section adapted to receivesaid staple fiber and a feed screw that extends the length of theextruder and feed section; said feed section defining an elongatedtangential side opening through which said staple fiber is introduced,and having a downwardly inclined surface that extends from saidtangential side opening and to a location tangentially adjacent saidfeed screw and adapted to conduct said staple fiber into the bite of thefeed screw as defined therebetween by the downwardly turning portion ofthe feed screw and said downwardly inclined surfaCe; said feed sectionfurther being jacketed and thereby adapted to be cooled by a circulatingfluid medium so that the feed section interior wall surface with whichthe staple fiber comes into contact is below the temperature at whichthe staple fiber would tend to stick to said interior wall surface; saidfeed section still further having a plurality of keyed wedges extendingradially inwardly from the interior wall surface of the feed section andcircumferentially spaced apart and spaced from said feed screw, saidkeyed wedges initially spiralling partly around and along a portion ofthe length of the feed section and then straightening out to extendparallel to and for the remainder of said length of the feed section,the keyed wedges adapted to cooperate with said feed screw to preventsaid staple fiber from rotating with said feed screw and to assurecontinuous forward feeding of the staple fiber from the tangential sideopening; said extruder having heating means extending along the lengthof the extruder forward of the feed section for melting said staplefiber into a melt flow and means for forcing cooling air around theoutside of the extruder so as to regulate the heat applied to the staplefiber; extrusion die means comprising an underwater pelletizer definingan inlet for receiving said melt flow, a die through which the melt flowis extruded, means for circulating a heated fluid through said die tomaintain a predetermined temperature, means for circulating a coolingfluid on the extrusion side of the die to cool the melt flow whenextruded through the die, shearing means for shearing melt flow intopellets when the melt flow is extruded through the die, and outlet meansadapted to conduct therethrough the extruded pellets and cooling liquidas a liquid slurry; means connecting the extruder and the extrusion diemeans and adapted to conduct said melt flow from one to the other; andmeans following the underwater pelletizer and adapted to receive saidliquid slurry from said outlet means and remove the liquid from and drysaid pellets.
 1. Apparatus for recovering waste thermoplastic fiber ofcontinuous length filamentary material and converting it into re-useablefeedstock, and comprising: means for converting said continuous lengthfilamentary material into staple fiber; storage means for receiving andstoring said staple fiber; conveyor means for moving said staple fiberto said storage means from said means for converting said continuouslength filamentary material; said storage means having an inlet throughwhich the staple fiber is received and an outlet through which thestaple fiber leaves the storage means, a conveyor means within thestorage means for moving the staple fiber from the inlet to the outlet;an extruder for compacting and melting said staple fiber; conveyor meansfor delivering said staple fiber to said extruder from said storagemeans; said extruder having at one end a feed section adapted to receivesaid staple fiber and a feed screw that extends the length of theextruder and feed section; said feed section defining an elongatedtangential side opening through which said staple fiber is introduced,and having a downwardly inclined surface that extends from saidtangential side opening and to a location tangentially adjacent saidfeed screw and adapted to conduct said staple fiber into the bite of thefeed screw as defined therebetween by the downwardly turning portion ofthe feed screw and said downwardly inclined surfaCe; said feed sectionfurther being jacketed and thereby adapted to be cooled by a circulatingfluid medium so that the feed section interior wall surface with whichthe staple fiber comes into contact is below the temperature at whichthe staple fiber would tend to stick to said interior wall surface; saidfeed section still further having a plurality of keyed wedges extendingradially inwardly from the interior wall surface of the feed section andcircumferentially spaced apart and spaced from said feed screw, saidkeyed wedges initially spiralling partly around and along a portion ofthe length of the feed section and then straightening out to extendparallel to and for the remainder of said length of the feed section,the keyed wedges adapted to cooperate with said feed screw to preventsaid staple fiber from rotating with said feed screw and to assurecontinuous forward feeding of the staple fiber from the tangential sideopening; said extruder having heating means extending along the lengthof the extruder forward of the feed section for melting said staplefiber into a melt flow and means for forcing cooling air around theoutside of the extruder so as to regulate the heat applied to the staplefiber; extrusion die means comprising an underwater pelletizer definingan inlet for receiving said melt flow, a die through which the melt flowis extruded, means for circulating a heated fluid through said die tomaintain a predetermined temperature, means for circulating a coolingfluid on the extrusion side of the die to cool the melt flow whenextruded through the die, shearing means for shearing melt flow intopellets when the melt flow is extruded through the die, and outlet meansadapted to conduct therethrough the extruded pellets and cooling liquidas a liquid slurry; means connecting the extruder and the extrusion diemeans and adapted to conduct said melt flow from one to the other; andmeans following the underwater pelletizer and adapted to receive saidliquid slurry from said outlet means and remove the liquid from and drysaid pellets.
 2. Apparatus for recovering an entangled mass of wastethermoplastic fiber of continuous length filamentary material andconverting it into re-usable feed stock, and comprising: means forcompressing said entangled mass of continuous length filamentarymaterial into a mass of predetermined size; means for cutting said massof predetermined size into sections of predetermined size, and furthermeans for cutting said sections into staple fiber; extruder means formechanically compacting and melting said staple fiber into a melt flow,and extruding said melt flow into said re-useable feedstock; saidextruder means having a barrel and a feed screw rotatable within saidbarrel, said barrel having connected at one end an extrusion die meansand at the other end including a feed section, and being provided withheating means along its length; said feed section defining an elongatedtangential side opening through which said staple fiber is introducedinto the bite of the feed screw, as defined therebetween by thedownwardly turning portion of the feed screw and the interior wall ofthe barrel; and means for feeding said staple fiber to and into saidtangential side opening and into the bite of the feed screw therebyentrapping the staple fiber on the underside of the feed screw andincluding means for controlling and metering the feed of said staplefiber; said feed section further including therewithin means forpreventing said staple fiber from rotating with said feed screw andthereby adapted to enable and assure continuous forward movement of thestaple fiber from the feed section to said extrusion die means. 3.Apparatus according to claim 2, and wherein the extruder means furthercomprises: means for internally cooling said feed section of the barrelso that the feed section interior wall surface with which the staplefiber comes into contact is below the tEmperature at which the staplefiber would tend to stick to said feed section interior wall surface. 4.Apparatus according to claim 2 and wherein said extrusion die meanscomprises an underwater pelletizer including a die, means located on oneside of the die to heat the die, and means on the other side of the dieto circulate heated water against the face of the die.
 5. Apparatusaccording to claim 2 and wherein said means for controlling and meteringthe feed of said staple fiber includes a storage bin adapted to receiveand store more staple fiber than can be fed directly to said extrudermeans for mechanically compacting and melting said staple fiber, saidstorage bin having inlet and outlet openings through which the staplefiber moves, and including therewithin conveyor means for moving thestored fiber from the inlet opening to the outlet opening and means forcontrolling the amount of staple fiber that moves through said outletmeans.
 6. Apparatus according to claim 2 and wherein said means forpreventing said staple fiber from rotating includes surfaces extendingradially inwardly from the interior wall of the feed section and beingcircumferentially spaced apart and adapted to cooperate with the flightson said feed screw to keep the movement of the mass of staple fibersperpendicular to the screw flights.
 7. Apparatus according to claim 2and wherein said means for preventing said staple fiber from rotatingincludes a keyed section extending radially inwardly from the interiorwall surface of the barrel and spaced from said feed screw, said keyedsection initially spiralling partly around and along a portion of thelength of the feed section and then straightening out to extend parallelto and for the remainder of said length of the feed section. 8.Apparatus according to claim 2 and wherein said means for preventingsaid staple fiber from rotating includes a plurality of keyed wedgesextending radially inwardly from the interior wall surface of said feedsection and circumferentially spaced apart and spaced from said feedscrew, said keyed wedges each initially spiralling partly around andalong a portion of the length of the feed section and then straighteningout to extend parallel to and for the remainder of said length of thefeed section.
 9. Apparatus according to claim 7 and wherein said feedscrew has substantially coextensive with said tangential side opening afirst section having a root diameter of constant size, the interior wallsurface adjacent to said first section and to said side opening taperinginwardly toward said feed screw and thereby adapted in cooperation withsaid feed screw to initiate compression of said staple fiber. 10.Apparatus according to claim 7 and wherein a downwardly inclined surfaceextends from said elongated tangential side opening toward said bite ofthe feed screw, said inclined surface adapted to conduct said staplefiber into said bite when the fiber is introduced into said sideopening.
 11. Apparatus according to claim 2 and wherein said tangentialside opening has a length about three times the diameter of the feedscrew.